Galadriel aided by Nenya... as powerful as Melian?

[Voralphion]

the most powerful Elf to have ever lived in Middle-Earth.

What about Luthien, who is said to be the most powerful of all the eldar, and was so powerful that she was able to put Morgoth to sleep so that Beren could steal the Silmaril.
Also as mentioned earlier she contributed to defeating Sauron and threw down the walls of Tol-in-Gaurhoth by breaking the spell that Sauron placed on the stones.